Subpanel location question

I'm planning for a spa. My panel is full, and there's no opportunity to replace existing breakers with tandems (have them already). It's just plain full. I need two, 25A feeders from the panel for the spa GFCI (50A)... or two "slots". The space just isn't there.

The only option I can think of is a subpanel. But unlike most other forum posters, I'm not putting this in a garage, basement or closet. I assume you can install a subpanel on an exterior wall near the main panel, as long as it meets the spacing req's... 36" depth, 30" width, etc.? I'd have to put it about 5 feet to the side of the main panel. Something like this Eaton 34824 125 Amp, 6 Spaces, 12 Circuit Outdoor Main Lug Load Center: I'll consult an electrician, but I assume you cannot tie this load center directly into the main panel bus bar... and that this 125A sub-panel will require feeders also? If it does, then I would have to re-locate some load from the main panel and distribute through this new sub-panel.

Swapping the main panel for a larger one sounds like a bigger job than adding a sub-panel, but maybe not after all is said and done.

A sub-panel is just that, a panel powered by a main panel. So, the power into that subpanel must come through a breaker(s) in the main panel. Depending on the age and brand of current panel, there may be a good reason to install a new, larger one. Depending on your service drop, with the additions, it may be a good idea to upgrade the service to a higher amperage, but that would depend on what you have and your planned total load.

WHen I had my kitchen redone, I wanted individual breakers for all of the appliances and to separate some of the things that had been ganged in the old one. The new subpanel is right next to the main, and actually has about twice the space in it. Depends on how much room you have where the original is where the best location for the new one is.